Field of the Invention
The present invention relates to a driving device for a hybrid working machine provided with an engine and a generator motor to be driven by the engine.
Description of the Background Art
Conventionally, there has been known a hybrid excavator including an engine, a generator motor driven by the engine, and a hydraulic pump. The engine and the power generator constitute a power unit as a driving device to drive the hydraulic pump so as to make the hydraulic pump discharge hydraulic fluid, whose pressure operates a hydraulic actuator. The generator motor exhibits both of a generator function and a motor function. The generator function is converting the engine power outputted from the engine into electric power, which is charged in a capacitor. The motor function is converting the electric power accumulated in the capacitor into motor power, which assists a drive of the engine.
The engine has a crank shaft for outputting the generated engine power, and the generator motor has a rotor shaft for receiving an input of the engine power. As disclosed in e.g. Japanese Unexamined Patent Publication No. 2008-7023, the crank shaft and the rotor shaft are interconnected through a flywheel. The interconnection is performed, for example, as follows: the crank shaft, the flywheel, and the rotor shaft are coaxially aligned in such a manner that a flange surface of the crank shaft and one of the flange surfaces of the flywheel are opposed to each other and that the other of the flange surfaces of the flywheel and a flange surface of the rotor shaft face are opposed to each other; and the adjacent ones of the crank shaft, the flywheel, and the rotor shaft are fastened to each other by bolts.
Such an interconnection requires an axial alignment of coaxially aligning the members to be connected in order to suppress vibrations of the shaft at the time of rotation thereof. Conventionally, as a measure for axial alignment, there has been generally used a method of providing a convex portion to one of two flange surfaces to be connected to each other and providing a concave portion to the other, on respective entire circumferences thereof, and fitting the convex portion with the concave portion. This method, however, requires securing a proper clearance for the fit between the convex portion and the concave portion, by which an axial displacement amount may be increased to thereby make it difficult to sufficiently suppress vibrations of the shaft at the time of high-speed rotation thereof. This drawback is conspicuous especially in a horizontally mounted driving device in which a crank shaft, a flywheel, and a rotor shaft are horizontally aligned and interconnected to each other. On the other hand, setting the clearance to a value as small as possible or additionally providing a positioning pin to suppress the axial displacement amount makes it difficult to perform an assembling operation.